Canning - food preservation - help

I would like to know if what I have done is not going to harm anyone with food borne issues.

I followed a recipe to make antipasto. Besides vegies, there is canned baby shrimp in the mix. I boiled all jars and lids and then scooped the simmering mix into the jars. Then, I put the lids and metal rings tightly on the jars and baked them in the oven at 250 degrees for 2-hours. When I removed the jars from the oven the lids started to seal down ( I could hear them). After about 15 mins or so all the jars had sealed.

My question: Should I have used a canner for this, or am I okay with what I did?